Calibration technique

Abstract

The tolerance of Short-Open-Load (SOL) and Short-Open-Load-Reflect (SOLR) VNA calibration for variability in probe position is improved by using load and short calibration structures having impedance elements with a length at least two times the probe contact pitch and a width at least two times the sum of the combined pitches of the probe contacts.

1 . A method for calibrating a probing system including a probing element comprising a first contact and a second contact spaced apart from said first contact by a pitch on a contact axis, said method comprising the steps of:
 (a) measuring a result of a stimulation of a first calibration standard with a signal, said first calibration standard comprising a short circuit between said first contact and said second contact;   (b) measuring a result of a stimulation of a second calibration standard with a signal, said second calibration standard comprising an open circuit between said first contact and said second contact;   (c) measuring a result of a stimulation of a third calibration standard with a signal, said third calibration standard comprising a substantially planar resistor having a surface simultaneous engageable by said first contact and said second contact, said planar resistance element having a first dimension, measured approximately parallel to said contact axis, of at least twice said pitch and a second dimension, measured substantially normal to said contact axis, of at least twice said pitch; and   (d) using said result of said stimulation of said first calibration structure, said result of said stimulation of said second calibration structure, and said result of said stimulation of said third calibration structure to formulate an error model for said probing system.   
   
   
       2 . The method for calibrating a probing system of  claim 1  wherein a resistance between two points separated by a distance equal to said pitch at a first location on said surface of said resistance element is substantially equal to a resistance between two points separated by a distance equal to said pitch at a second location on said surface of said resistance element. 
   
   
       3 . The method for calibrating a probing system of  claim 1  wherein a resistance between two points separated by a distance equal to said pitch at a first location on said surface of said resistance element is substantially different than a resistance between two points separated by a distance equal to said pitch at a second location on said surface of said resistance element. 
   
   
       4 . The method for calibrating a probing system of  claim 1  wherein said surface of said resistance element comprises at least one non-conductive region having an area less than an area of said first contact. 
   
   
       5 . The method for calibrating a probing system of  claim 1  wherein the surface of said first calibration region having an area less than an area of said first contact. 
   
   
       6 . The method for calibrating a probing system of  claim 1  wherein the surface said first calibration region is patterned. 
   
   
       7 . The method for calibrating a probing system of  claim 1  wherein said planar resistance element is affixed to a surface of a substrate and said first calibration standard comprises a substantially planar conductive element affixed to said surface of said substrate. 
   
   
       8 . The method for calibrating a probing system of  claim 1  wherein said first calibration standard comprises a substantially planar conductive element having a first dimension of at least twice said pitch measured approximately parallel to said contact axis and a second dimension at least twice said pitch measured substantially normal to said contact axis. 
   
   
       9 . The method for calibrating a probing system of  claim 1  further comprising the steps of:
 (a) measuring a result of a first stimulation of a fourth calibration standard by a signal transmitted from said first contact of said probe, said fourth calibration standard comprising a path having first terminal engageable by said first contact of said probe and a second terminal engageable by a contact of a second probe;   (b) measuring a result of a second stimulation of said fourth calibration standard by a signal transmitted from said contact of said second probe; and   (c) using said result of said first stimulation of said fourth calibration standard, said second stimulation of said fourth calibration standard, said result of said stimulation of said first calibration structure, said result of said stimulation of said second calibration structure, and said result of said stimulation of said third calibration structure to formulate another error model for said probing system.   
   
   
       10 . The method for calibrating a probing system of  claim 9  wherein a resistance between two points separated by a distance equal to said pitch at a first location on said surface of said resistance element is substantially equal to a resistance between two points separated by a distance equal to said pitch at a second location on said surface of said resistance element. 
   
   
       11 . The method for calibrating a probing system of  claim 9  wherein a resistance between two points separated by a distance equal to said pitch at a first location on said surface of said resistance element is substantially different than a resistance between two points separated by a distance equal to said pitch at a second location on said surface of said resistance element. 
   
   
       12 . The method for calibrating a probing system of  claim 9  wherein said planar resistance element is affixed to a surface of a substrate and said first calibration standard comprises a substantially planar conductive element affixed to said surface of said substrate. 
   
   
       13 . The method for calibrating a probing system of  claim 9  wherein said first calibration standard comprises a substantially planar conductive element having a first dimension of at least twice said pitch measured approximately parallel to said contact axis and a second dimension at least twice said pitch measured substantially normal to said contact axis. 
   
   
       14 . A method for calibrating a probing system including a probing element comprising at least three contacts, including a signal contact and a ground contact, spaced along a contact axis, each contact separated from an adjacent contact by a pitch, said method comprising the steps of:
 (a) measuring a result of a stimulation of a first calibration standard with a signal transmitted from said signal contact, said first calibration standard comprising a short circuit between said signal contact and said ground contact;   (b) measuring a result of a stimulation of a second calibration standard with a signal transmitted from said signal contact, said second calibration standard comprising an open circuit between said signal contact and said ground contact;   (c) measuring a result of a stimulation of a third calibration standard with a signal transmitted from said signal contact, said third calibration standard comprising a substantially planar resistance element having a surface simultaneous engageable by said signal contact and said ground contact, said planar resistance element having a first dimension, measured approximately parallel to said contact axis, of at least twice a sum of said pitches separating said contacts of said probe and a second dimension, measured substantially normal to said contact axis, at least twice said pitch; and   (d) using said result of said stimulation of said first calibration structure, said result of said stimulation of said second calibration structure, and said result of said stimulation of said third calibration structure to formulate an error model for said probing system.   
   
   
       15 . The method for calibrating a probing system of  claim 14  wherein a resistance between two points separated by a distance equal to said pitch at a first location on said surface of said resistance element is substantially equal to a resistance between two points separated by a distance equal to said pitch at a second location on said surface of said resistance element. 
   
   
       16 . The method for calibrating a probing system of  claim 14  wherein a resistance between two points separated by a distance equal to said pitch at a first location on said surface of said resistance element is substantially different than a resistance between two points separated by a distance equal to said pitch at a second location on said surface of said resistance element. 
   
   
       17 . The method for calibrating a probing system of  claim 14  wherein said planar resistance element is affixed to a surface of a substrate and said first calibration standard comprises a substantially planar conductive element affixed to said surface of said substrate. 
   
   
       18 . The method for calibrating a probing system of  claim 14  wherein said first calibration standard comprises a substantially planar conductive element having a first dimension, measured approximately parallel to said contact axis, of at least twice a sum of said pitches separating said contacts of said probe and a second dimension, measured substantially normal to said contact axis, at least twice said pitch. 
   
   
       19 . The method for calibrating a probing system of  claim 14  further comprising the steps of:
 (a) measuring a result of a first stimulation of a fourth calibration standard by a signal transmitted from said signal contact of said probe, said fourth calibration standard comprising a path having first terminal engageable by said signal contact of said probe and a second terminal engageable by another signal contact of the probing element;   (b) measuring a result of a second stimulation of said fourth calibration standard by a signal transmitted from said another signal contact of said probe; and   (c) using said result of said first stimulation of said fourth calibration standard, said second stimulation of said fourth calibration standard, said result of said stimulation of said first calibration structure, said result of said stimulation of said second calibration structure, and said result of said stimulation of said third calibration structure to formulate another error model for said probing system.   
   
   
       20 . The method for calibrating a probing system of  claim 16  wherein a resistance between two points separated by a distance equal to said pitch at a first location on said surface of said resistance element is substantially equal to a resistance between two points separated by a distance equal to said pitch at a second location on said surface of said resistance element. 
   
   
       21 . The method for calibrating a probing system of  claim 16  wherein a resistance between two points separated by a distance equal to said pitch at a first location on said surface of said resistance element is substantially different than a resistance between two points separated by a distance equal to said pitch at a second location on said surface of said resistance element. 
   
   
       22 . The method for calibrating a probing system of  claim 16  wherein said planar resistance element is affixed to a surface of a substrate and said first calibration standard comprises a substantially planar conductive element affixed to said surface of said substrate. 
   
   
       23 . The method for calibrating a probing system of  claim 16  wherein said first calibration standard comprises a substantially planar conductive element having a first dimension, measured approximately parallel to said contact axis, of at least twice a sum of said pitches separating said contacts of said probe and a second dimension, measured substantially normal to said contact axis, at least twice said pitch. 
   
   
       24 . A method for calibrating a probing system comprising a first contact and a second contact spaced apart from said first contact by a pitch on a contact axis, said method comprising the steps of:
 (a) measuring a result of a stimulation of a first calibration standard with a signal, said first calibration standard comprising a first electrical element between said first contact and said second contact;   (b) measuring a result of a stimulation of a second calibration standard with a signal, said second calibration standard comprising a second electrical element between said first contact and said second contact;   (c) measuring a result of a stimulation of a third calibration standard with a signal, said third calibration standard comprising a substantially planar resistor having a surface simultaneous engageable by said first contact and said second contact, said planar resistance element having a first dimension, measured approximately parallel to said contact axis, of at least twice said pitch and a second dimension, measured substantially normal to said contact axis, of at least twice said pitch;   (d) using said result of said stimulation of said first calibration structure, said result of said stimulation of said second calibration structure, and said result of said stimulation of said third calibration structure to formulate an error model for said probing system;   (e) wherein said planar resistance element has a contact resistance less than 20 ohms at zero frequency or greater.   
   
   
       25 . The system of  claim 24  wherein said contact resistance is less than 10 ohms. 
   
   
       26 . The system of  claim 25  wherein said contact resistance is less than 5 ohms. 
   
   
       27 . The system of  claim 24  wherein said contact resistance is at 2 GHz or greater. 
   
   
       28 . The system of  claim 24  wherein said contact resistance is at 20 GHz or greater. 
   
   
       29 . The system of  claim 24  wherein said contact resistance is at 50 GHz or greater. 
   
   
       30 . The system of  claim 26  wherein said contact resistance is at 2 GHz or greater. 
   
   
       31 . The system of  claim 26  wherein said contact resistance is at 20 GHz or greater. 
   
   
       32 . The system of  claim 26  wherein said contact resistance is at 50 GHz or greater. 
   
   
       33 . A method for calibrating a probing system comprising a first contact and a second contact spaced apart from said first contact by a pitch on a contact axis, said method comprising the steps of:
 (a) measuring a result of a stimulation of a first calibration standard with a signal, said first calibration standard comprising a first electrical element between said first contact and said second contact wherein said first electrical element is a generally unpatterned layer;   (b) measuring a result of a stimulation of a second calibration standard with a signal, said second calibration standard comprising a second electrical element between said first contact and said second contact wherein said second electrical element is a generally unpatterned layer;   (c) measuring a result of a stimulation of a third calibration standard with a signal, said third calibration standard comprising a substantially planar resistor having a surface simultaneous engageable by said first contact and said second contact, said planar resistance element having a first dimension, measured approximately parallel to said contact axis, of at least twice said pitch and a second dimension, measured substantially normal to said contact axis, of at least twice said pitch, wherein said resistance element is a generally unpatterned layer;   (d) using said result of said stimulation of said first calibration structure, said result of said stimulation of said second calibration structure, and said result of said stimulation of said third calibration structure to formulate an error model for said probing system.   
   
   
       34 . The system of  claim 33  wherein at least one of said unpatterned layers includes patterned structures that are independent of said pitch. 
   
   
       35 . The system of  claim 33  wherein said system includes a test socket. 
   
   
       36 . The system of  claim 35  wherein at least one of said unpatterned layers includes a generally rectangular region of at least one of said first electrical element, said second electrical element, and said resistance element. 
   
   
       37 . The system of  claim 33  wherein said resistive element includes conductive elements located in such a manner that they are coincident with said first and second contacts. 
   
   
       38 . The system of  claim 37  wherein said conductive elements are located in such a manner that are coincident with ten such said contacts. 
   
   
       39 . The system of  claim 33  wherein one of said first, second, and third calibration structures is supported by a wafer. 
   
   
       40 . The system of  claim 39  wherein at least two of said first, second, and third calibration structures are illustrated by a single wafer.